This invention relates to the dissipation of heat from heat generating objects.
Various areas exist in which heat conductors of very high thermal conductivity, hereinafter sometimes called "heat sinks", are necessary. These include electronic equipment, in which certain components generate heat. Another example is in repeating stations for fiber optic networks. Signals are transmitted by laser light over the fibers of such networks for very great distances. Since these signals decrease substantially in intensity over several kilometers, it is necessary to construct "repeating stations" periodically along the network, for the purpose of increasing the intensity of the light transmitted along the network. In a typical repeating station of this type, a photodetector is employed to convert the weakened signal transmitted by fiber optics to an electrical signal, which is then magnified, reconverted to a light signal by a light-emitting diode, and transmitted in turn along the next segment of the network.
In order to minimize the requisite number of repeating stations, optimum magnification of the signal in any station is desirable. However, the amount of radiant energy of any kind generated electrically is proportional to the fourth power of the current employed. While a portion of such radiant energy is in the form of light, the remainder thereof is lost as heat. In any individual station, therefore, very large amounts of heat are generated, requiring efficient heat sinks to maintain the operativeness of the repeating station.
Diamond is a promising material for use as a heat sink by reason of its very high thermal conductivity. This is particularly true of isotopically pure single crystal diamond, as disclosed in copending, commonly owned application Ser. No. 08/163,608.
However, several problems have been encountered in the use of diamond heat sinks. Natural diamond is prohibitively expensive for this purpose, or nearly so. The same is generally true of synthetic diamond prepared under high pressure-temperature conditions.
The production of polycrystalline diamond by chemical vapor deposition (hereinafter "CVD") in recent years has offered hope for a less expensive but still effective heat sink material. However, in addition to still being quite costly, CVD diamond is subject to stress cracking and other problems. Consequently, it has not gained wide use.